Reading adjustment for an indicating instrument in hermetically sealed cases



Mardl 1952 J. F. VEEVERS ETAL 2,587,668

READING ADJUSTMENT FOR AN INDICATING INSTRUMENT IN HERMETICALLY SEALEDCASES I Filed March 11. 1948 2 smE'rs-smw 1 INVENTORS A JouN FESTVe-svex:

l-l y (camv ERA/FR BY 3 FITSORNsY March 4, 1952 Filed March 11, 1948 J.F. VEEVE RS ET AL READING ADJUSTMENT FOR AN INDICATING INSTRUMENT INHERMETICALLY SEALED CASES 2 SHEETSSHEET 2 INVENToa; Jamv f-osn Vse'vsksA/Emar Gabe/v NANA-P latentecl Mar. 4, 1952 READING ADJUSTMENT FOR ANINDICAT- ING INSTRUMENT IN HERMETICALLY SEALED CASES John FosterVeevers, Lymm, and Henry Cobden Turner, Hale, England, assignors to TheGeneral Electric Gompany, Limited, London, England Application March 11,1948, Serial No. 14,324 In Great Britain January 3, 1947 6 Claims. 1

This invention is concerned with improvements in or relating toindicating instruments of the type which are fitted in, or providedwith, hermetically sealed cases.

One disadvantage of a completely sealed instrument is that the normalmethods of making adjustments to the position of the indicating member,for example, in order to set it to zero, cannot be used because of thedifficulty of making a satisfactory seal around the adjusting mechanismwhich will still permit the use thereof.

One object of this invention is to provide means by which adjustmentscan be made to the position of the indicating member when the instrumentis fitted in, or provided with, a. hermetically sealed case.

According to this invention in an indicating instrument, fitted in orprovided with a hermetically sealed case, an indicating member in saidinstrument can be adjusted from the outside of the case by thedisplacement of a flexible member such as a disc or diaphragm which issealed in a gastight manner to said case, displacements of v Figure 1shows in diagrammatic form a zero adjusting mechanism in accordance withthe first embodiment.

Figure 2 shows a sectional elevation of an instrument in accordance withthe second embodiment,

Figure 3 shows a plan view of the front cover of the instrumentillustrated in Figure 2, as seen from the section line III-III in Figure2, and

Figure 4 is a view of part of the movement of the instrument illustratedin Figure 2.

In the first embodiment shown in Figure 1, the position of a pointer isadjusted by displacement of one of the hairsprings [4 of the movement ofthe instrument, one end of this hairspring I l being attached to thelever l. The mechanism for causing movement of the lever I about itspivot 2 comprises a rod 3, which is soldered in an aperture in aflexible disc or diaphragm 4 itself soldered in an aperture in theinstrument case 5, joined to a double pawl 6 which co-operates with tworatchet wheels mounted on a common spindle, only one wheel 7 being inview in the figure. The claws 8 and 9 of the double pawl 6 lie inparallel planes and are rigidly mounted on a pivot I5 which is rotatablein a hole in a member I2 which locates the double pawl 5 relative to theratchet wheels. The claw 8 engages with the ratchet Wheel I whilst theclaw 9 engages with the other ratchet wheel, the teeth of which face inthe reverse direction to those on the ratchet wheel "I. A pin it on oneside of the ratchet wheel l slides in a slot II in the lever i, so thatrotation of the ratchet wheel 1 causes movement of the lever I about itspivot 2, the direction of which movement is dependent upon the directionof rotation of the ratchet wheel 7.

The rod 3 is connected to the claw 8 so that it is off-center to thepivot i5. The effect of this off-center connection is that if the rod 3is moved so that the diaphragm'd is flexed inwards, the claw 8 engageswith the ratchet wheel I and causes both ratchet wheels to revolve in aclockwise direction, whilst if the rod 3 is moved so that the diaphragmi is flexed outwards the claw 9 engages with the other ratchet wheel andcauses both ratchet wheels to revolve in an anticlockwise direction. Toobtain movement of the ratchet wheels greater than that corresponding toone tooth pitch, the rod 3 and therefore the diaphragm secured thereto,will have to be moved backwards and forwards a number of times, and thedirection of rotation of the ratchet wheels will'depend upon whether theto-and-fro oscilla- "tions of the diaphragm 4 are to one side or theother of "the unflexed position of the diaphragm l.

Rotation of the ratchet wheels will, through the lever I, cause movementof the pointer l3 of the instrument in a direction dependent upon thedirection of rotation of the ratchet wheel 7.

In the second embodiment of the invention shown in Figures 2, 3 and 4,the instrument case 5 is provided with a front cover I! which issoldered to the case 5' as shown at 6 to form a hermetically sealed casefor the instrument movement [9, which is of the well-known moving coiltype and need not be described further for the purposes of thisspecification.

A flexible diaphragm 4' is sealed by soldering as shown at l 8 to theoutside of the cover I! over an aperture 20 therein, the diaphragm 4'being fitted centrally with a tapered member 2 l which projects into theinterior of the case 5'. A circular plate 22 is fixed to the inside ofthe front cover I I over the aperture 20, and is formed with a circularhole 23 therein through which the tapered member 2| can pass. A lever 24pivoted atone end 25 on the circular plate 22 slightly overlaps thecircular hole 23. On the free end of the lever 24 is pivoted a pawl 6'which is held in engagement with a ratchet wheel 1' by the leaf spring26. A pin I0 fixed to the ratchet wheel I engages in a slot in thezero-adjuster arm I on the instrument movement 19.

The pointer I3 is carried on a spindle 21 which is mounted at each endby means of a jewel bearing 28 carried by a screw 29 which screws into ahole in a bridge piece 30 and is locked in position by means of a nut3|. One of the hairsprings H of the instrument movement is attached atits inner end to the spindle 2'! and at its outer end to the arm I, sothat rotation of the arm l about the spindle 21 varies the zeroadjustment of the pointer l3.

To alter the zero-adjustment of the instrument from outside the sealedcase the diaphragm 4' is pressed inwards. This causes the tapered member2| to pass through the circular hole 23 and move the lever 24 sidewaysabout its pivoted end 25, which causes the pawl -6' to move sidewaysalso, and thus the ratchet wheel I rotates. When pressure is removedfrom the diaphragm 4', the pressure of the spring 26 will restore thepawl 6' and the lever 24 to their original positions. It will beunderstood that the pin 10' will describe a circular path about thecentre of the spindle of the ratchet wheel I as the diaphragm 4' ismoved backwards and forwards by varying or intermittent pressurethereon. This means that the movement of the pin it! in the slot in thearm I will in one complete revolution of the ratchet wheel I first causethe arm I, and hence the pointer 53, to move in one direction, and thenin the other direction. Thus if the position of the pointer I3 isover-corrected when moving in one direction under the control of thezero adjuster, movement of the diaphragm 4 must be continued so that thepointer I3 changes its direction of movement and can be set to therequired position.

We claim:

1. In combination, a hermetically sealed case, said case having anopening therein, an indicating instrument within said case, saidinstrument including an indicating member within said case,

within said case for adjusting the position of said indicating member, aflexible member sealed over said opening, and a positive kinematicconnection between said flexible member and said movable member wherebydisplacements of the flexible member will be mechanically transmitted tothe movable member.

2. The combination according to claim 1, in which the movable member iscomprised by a pivoted lever adapted to rotate through a limited angle.

3. The combination according to claim 1, in which the positive kinematicconnection between the flexible member and the movable member includes apawl and a ratchet wheel engageable by said pawl, means to connect saidpawl to said flexible member, and means to connect said ratchet wheel tosaid movable member whereby displacement of said flexible member causesmovement of said pawl and consequent rotation of said ratchet wheel tovary the position of said movable member.

4. The combination according to claim 1 in which the flexible member isprovided with a projecting extension whereby movement of said projectingextension is transmitted to said flexible member.

5. In combination, a hermetically sealed case,-

said case having an aperture therein, an indicating instrument withinsaid case, said instrument being provided with an indicating member,spring means determining the non-indicating position of said indicatingmember, a ratchet wheel, said spring means being connected to saidratchet wheel, a pawl engageable with said ratchet wheel, a flexibledisc sealed over said aperture, and means to connect said disc to saidpawl whereby displacement of said disc causes movement of said pawl andconsequent rotation of said ratchet which through said spring meansvaries the nonindicating position of said indicating member.

6. The combination according to claim 5, in which the spring means isconnected to the ratchet wheel by a pin secured to said ratchet wheelwhich engages in a slot in a pivoted member to which said spring meansis attached, the length of said slot being greater than the diameter ofthe circle traced out by said pin during one revolution of the ratchetwheel, whereby the indicating member moves in one direction duringsubstantially one half of a revolution of the ratchet wheel and moves inthe opposite direction during the remainder of said revolution. saidinstrument also including a movable member 1 JOHN FOSTER VEEVERS. HENRYCOBDEN TURNER.

REFERENCES CITED UNITED STATES PATENTS Number Name Date Beckert July 15,1924

